Flush toilet

ABSTRACT

There is provided a flush toilet which can prevent scattering of flush water to the outside of a toilet bowl. The flush toilet includes: a toilet bowl having an erected surface part formed extending in a vertical direction at an upper end part of the toilet bowl and a bowl surface part formed below the lower end of the erected surface part to an inner circumferential side, and a water discharge port opened in the erected surface part and intended to discharge flush water into the toilet bowl. The flush water flows so as to form at least two water streams: a main stream flowing in a peripheral edge of the toilet bowl along the erected surface part and a branch stream branching from the main stream and running down to the bowl surface part side.

CROSS-REFERENCE TO RELATED APPLICATIONS

This application is a U.S. national stage patent application under 35U.S.C. 371 of International Application No. PCT/JP2017/039972, filedNov. 6, 2017, which claims priority to Japanese Application No.2016-252706, filed Dec. 27, 2016, each of which are hereby incorporatedby reference in the present disclosure in its entirety.

FIELD OF THE INVENTION

The present disclosure relates to a flush toilet.

BACKGROUND OF THE INVENTION

Patent Literature 1 discloses a flush toilet including: a toilet bowlhaving an erected surface part formed extending in the verticaldirection at the upper end of the toilet bowl and a bowl surface partformed below the lower end of the erected surface part to the innercircumferential side; and a water discharge port opened in the erectedsurface part and intended to discharge a flush water into the toiletbowl. This flush toilet is configured in such a manner that the flushwater discharged from the water discharge port flows in the peripheraledge of the toilet bowl to wash the inside of the toilet bowl anddischarges excrement in the toilet bowl. In addition, the flush waterflowing in the peripheral edge of the toilet bowl gradually runs downfrom the peripheral edge to the bowl surface part side so that thesurface of the bowl surface part is also washed.

Patent Literature 1: JP 2015-68164 A

SUMMARY OF THE INVENTION

In the case of the flush toilet as described above, a part of the flushwater that has run down to the bowl surface part side passes through thebowl surface part due to the water force, the centrifugal force or thelike, and joins again the flow in the peripheral edge of the toiletbowl. In this case, depending on the timing or the position of thejoining, the flush water may arrive at a position higher than the heightof the erected surface part and may scatter to the outside of the toiletbowl.

The present invention has been made in view of the above-describedconventional circumstances, and an object to be solved by the inventionis to provide a flush toilet capable of preventing scattering of flushwater.

A flush toilet of the present invention includes:

-   -   a toilet bowl having an erected surface part formed extending in        a vertical direction at an upper end part of the toilet bowl and        a bowl surface part formed below a lower end of the erected        surface part to an inner circumferential side, and    -   a water discharge port opened in the erected surface part and        intended to discharge flush water into the toilet bowl,    -   wherein the flush water flows so as to form at least two water        streams: a main stream flowing in a peripheral edge of the        toilet bowl along the erected surface part and a branch stream        branching from the main stream and running down to the bowl        surface part side,    -   wherein the branch stream joins the main stream at a joining        part on a downstream side, and    -   wherein the main stream arrives at the joining part earlier than        the branch stream.

BRIEF DESCRIPTION OF THE DRAWINGS

The invention will now be described, by way of example only, withreference to the accompanying drawings, in which:

FIG. 1 is a plan view showing a flush toilet according to someembodiments;

FIG. 2 is a perspective view showing a flush toilet according to someembodiments;

FIG. 3 is a cross-sectional view taken along line III-III of FIG. 1according to some embodiments;

FIG. 4 is a cross-sectional view taken along line IV-IV of FIG. 1according to some embodiments;

FIG. 5 is a diagram for explaining the action of a flush toiletaccording to some embodiments;

FIG. 6 is a diagram for explaining the action of a flush toiletaccording to some embodiments;

FIG. 7 is a diagram for explaining the action of a flush toiletaccording to some embodiments; and

FIG. 8 is an enlarged view of a main part of FIG. 7 according to someembodiments.

DETAILED DESCRIPTION OF THE INVENTION

In some embodiments, the flush water discharged from the water dischargeport flows having two water streams, i.e., the main stream and thebranch stream, and these two streams join at the joining part on thedownstream side. Among the two water streams, the main stream, which isa water stream along the erected surface part, arrives at the joiningpart earlier than the branch stream at the beginning of discharge of theflush water. For this reason, the water stream composed of the mainstream is formed in advance at the joining part before the branch streamjoins the main stream. As a result, the branch stream flowing from thecentral direction of the toilet bowl toward the outer circumferentialdirection (the outward direction of the toilet bowl) can be pressed downby the main stream flowing in the peripheral edge of the toilet bowlalong the erected surface part.

Therefore, the flush toilet of the present disclosure can preventscattering of flush water to the outside of the toilet bowl.

In some embodiments, the joining part may be located on a downstreamside of a region where a height of the main stream is maximum on a frontside of the toilet bowl. In this case, it is possible to prevent thebranch stream from affecting the maximum height of the main stream. Themain stream flowing in the peripheral edge of the toilet bowl flowswhile changing its height due to the water force, the change incurvature in the peripheral edge of the toilet bowl, and the like. Ifthe branch stream joins the main stream in the region where the heightof the main stream is maximum or on the upstream side of the region, thewater amount, water force, and the like of the branch stream may affectso that the height of the water stream may exceed the height of theerected surface part. However, the branch stream is caused to join themain stream on the downstream side of the region where the height of themain stream is maximum, thereby making it possible to prevent theinfluence of these factors. Accordingly, scattering of flush water canbe reliably prevented.

In some embodiments, the toilet bowl may have a recessed part which isprovided at the lower end of the bowl surface part and continued to adrain pipe. The bowl surface part may be formed to be inclined in such amanner that the branch stream after a beginning of discharge from thewater discharge port is dropped into the recessed part on an imaginaryline connecting the water discharge port and the region where the heightof the main stream is maximum in a plan view. In this case, since it ispossible to suppress the water amount and the water force of a componentof the branch stream that tends to flow on the imaginary line,scattering of flush water can be reliably prevented. Further, it ispossible to easily adjust the water force and the flow rate of thecomponent of the branch stream that tends to flow on the imaginary lineaccording to the inclination angle of the bowl surface part, so that thewater force or the height of the water stream after joining can beeasily adjusted, with the result that scattering of flush water can bereliably prevented.

In some embodiments, a moving distance of the branch stream in a periodfrom when the branch stream branches from the main stream to when thebranch stream arrives at the joining part may be set to be longer than amoving distance of the main stream in a period from when the branchstream branches therefrom to when the main stream arrives at the joiningpart. In this case, the main stream can be reliably caused to arrive atthe joining part earlier than the branch stream.

In the following description, as for a front-back direction, the lowerside in FIG. 1 and the left side in FIG. 3 are each defined as a frontside. As for a lateral direction, the left and right sides in FIG. 1 aredefined as left and right sides as they are. A flush toilet 1 of thepresent embodiment includes a toilet bowl 10 and water discharge ports21, 22.

As shown in FIGS. 1 to 3, the toilet bowl 10 has an erected surface part11, a bowl surface part 12, a shelf surface part 13, and a recessed part14. The erected surface part 11 is provided at the upper end part of thetoilet bowl 10, and the surface thereof is formed extending in thevertical direction. The erected surface part 11 is formed oversubstantially the entire circumference of the upper end part of thetoilet bowl 10. The erected surface part 11 is formed in an annularshape slightly longer in the front-back direction in a plan view and hasan egg shape in which the curvature of the front part is larger thanthat of the rear part. The upper end surface of the erected surface part11 extends outward and substantially horizontally at a substantiallyconstant height. Thus, the flush toilet 1 is a toilet having nooverhanging part projecting inward from the upper end of the erectedsurface part 11.

The bowl surface part 12 is formed in a mortar shape below the lower endof the erected surface part 11 to the inner circumferential side. Thebowl surface part 12 is formed inclined so as to be lower toward thecenter rear side. The shelf surface part 13 is provided between theerected surface part 11 and the bowl surface part 12 so as to connectthe lower end of the erected surface part 11 and the upper end of thebowl surface part 12. The shelf surface part 13 has a surface facingupward, and extends slightly inclining downward as it goes inward. Theshelf surface part 13 is provided in a peripheral edge of the toiletbowl 10 except a part of the front side, and is formed in asubstantially horseshoe shape in a plan view. The recessed part 14 isformed below the bowl surface part 12 and continued to a drain pipe 30.The recessed part 14 is provided continuously with the lower end of thebowl surface part 12. The recessed part 14 is disposed at substantiallythe center in the lateral direction and near the rear side of the toiletbowl 10. In the recessed part 14, reserved water composed of flush wateris formed.

The water discharge ports 21, 22 are opened in the erected surface part11 of the toilet bowl 10 and discharge the flush water into the toiletbowl 10. In some embodiments, two water discharge ports, i.e., the firstwater discharge port 21 and the second water discharge port 22 areprovided as the water discharge ports. The two water discharge ports 21,22 each discharge the flush water into the toilet bowl 10. Thedischarged flush water flows on the shelf surface part 13 and the bowlsurface part 12 within the toilet bowl 10 while swirlingcounterclockwise, flows into the recessed part 14, and is discharged tothe drain pipe 30.

Specifically, the first water discharge port 21 is provided opened onthe left rear side of the toilet bowl 10. The flush water dischargedfrom the first water discharge port 21 is discharged onto the shelfsurface part 13 toward the front side, and a part thereof becomes a partof a main stream F1, as will be described later, which flows in theperipheral edge of the toilet bowl 10 along the erected surface part 11.Another part of the flush water becomes a part of a branch stream F2, aswill be described later, which runs down from the shelf surface part 13to the bowl surface part 12 side. Still another part of the flush waterbecomes a part of a second water stream F4, as will be described later,which flows into the recessed part 14.

The second water discharge port 22 is provided opened on the right rearside of the toilet bowl 10. The flush water discharged from the secondwater discharge port 22 is discharged toward the left side slightly tothe front side, and a part thereof joins the flush water discharged fromthe first water discharge port 21. The other part becomes a part of thesecond water stream F4 which runs down to the bowl surface part 12 sideand flows into the recessed part 14. In the flush toilet 1 according tosome embodiments, the amount of flush water to be used in one flush isset to about 5 liters. The flush water in the amount for one flush isstored in a tank (not shown) in advance. The discharge flow rate (amountof water to be discharged per unit time) of the flush water is almostmaximum at the beginning of discharge, and then gradually decreases.

As shown in FIGS. 1 and 2, the flush water flows so as to form mainlyfour water streams F1 to F4 in the toilet bowl 10. Among these waterstreams, the main stream F1 and the branch stream F2 are water streamsthat are discharged from the water discharge ports 21, 22 and swirlwithin the toilet bowl 10. The first water stream F3 and the secondwater stream F4 are water streams that run down into the recessed part14.

The flush water discharged from the water discharge ports 21, 22 formsat least two water streams, i.e., the main stream F1 and the branchstream F2, and washes the inside of the toilet bowl 10. That is, a partof the flush water flows so as to form the main stream F1 and the branchstream F2. Among these water streams, the main stream F1 is a waterstream that flows in the peripheral edge of the toilet bowl 10 along theerected surface part 11. The branch stream F2 is a water stream thatbranches from the main stream F1 and runs down to the bowl surface part12 side. The branch stream F2 joins the main stream F1 at a joining partJ on the downstream side. In the flush water forming these two waterstreams F1, F2, the main stream F1 arrives at the joining part J earlierthan the branch stream F2. In detail, the branch stream F2 branches fromthe main stream F1, flows down to the bowl surface part 12 side therebywashing the surface of the bowl surface part 12, and flows into therecessed part 14, whereas a part of the branch stream F2 joins the mainstream F1 at the joining part J on the downstream side. Among the mainstream F1 and branch stream F2 joining at the joining part J, the mainstream F1 that first arrives at the joining part J immediately after thebeginning of discharge of the flush water into the toilet bowl 10arrives earlier than the branch stream F2 that first arrives at thejoining part J immediately after the beginning of discharge.

In some embodiments, such joining configuration of the main stream F1and the branch stream F2 is realized by adjusting the flow distance ofthe branch stream F2 by recessing deeply downward the surface of thebowl surface part 12 which serves as a flow path to the joining part Jof the branch stream F2. That is, as shown in FIGS. 3 to 5, the surfaceheight of a portion of the bowl surface part 12 where the branch streamF2 flows is made sufficiently deeper than the flow height of the mainstream F1 (height of the shelf surface part 13), whereby the movingdistance of the branch stream F2 is set to be longer. That is, thelength of the moving distance of the branch stream F2 is set byutilizing the height difference in a period from when the branch streamF2 branches from the main stream F1 at the height of the shelf surfacepart 13 to when it joins again the main stream F1 in the joining part Jat the height of the shelf surface part 13. In some embodiments, themoving distance of the branch stream F2 in a period from when itbranches from the main stream F1 to when it arrives at the joining partJ is set to be longer than the moving distance of the main stream F1 ina period from when the branch stream F2 branches therefrom to when themain stream F1 arrives at the joining part J. Further, due to the heightdifference thus provided between the surface of the bowl surface part 12and the surface of the shelf surface part 13, the water force of thebranch stream F2 is weakened, whereby flow rate is reduced. This alsoaffects the arrival timing of the branch stream F2 at the joining partJ.

The joining part J is located on the downstream side of a region A whichis located on the front side of the toilet bowl 10 and where the heightof the main stream F1 is maximum. As shown in FIG. 6, the main stream F1flowing along the erected surface part 11 in the peripheral edge of thetoilet bowl 10 is pressed against the erected surface part 11 in theouter circumferential direction under the influence of the centrifugalforce. The main stream F1 flows while changing its height according tothe change in curvature of the erected surface part 11 and the flowrate. In FIG. 6, an imaginary line denoted by symbol M indicates atrajectory of the maximum arrival height of the flow which shows theposition where the flow in the peripheral edge of the toilet bowl 10flows the highest on the surface of the erected surface part 11 duringthe flushing. In the trajectory, the portion where the height of themain stream F1 is maximum on the front side of the toilet bowl 10 is theregion A. If the branch stream F2 joins in this region A, the flushwater may reach a much higher position and may scatter outside thetoilet bowl 10. Therefore, in some embodiments, the position of thejoining part J is set on the downstream side of the region A. In someembodiments, since the region A where the height of the main stream F1is maximum is located at a rightward position on the front side of thetoilet bowl 10, the joining part J is set to be located on a furtherdownstream side of the position, as shown in FIG. 6.

In some embodiments, the portion where the height of the flow in theperipheral edge of the toilet bowl 10 is maximum on the front side ofthe toilet bowl 10 is the region A where the height of the main streamF1 is maximum. However, the flow may be maximum at the joining part Jdue to joining of the branch stream F2.

In some embodiments, the bowl surface part 12 is inclined in such amanner that the branch stream F2 immediately after the beginning ofdischarge from the water discharge port 21 is dropped into the recessedpart 14 on an imaginary line V connecting the water discharge port 21and the region A where the height of the main stream F1 is maximum in aplan view, as shown in FIG. 6. Specifically, as shown in FIG. 4, theinclination angles θ1, θ2 of the surface of the bowl surface part 12 areset to 45° or more (more preferably 60° or more). Further, in someembodiments, the inclination angle θ1 of the surface on the left side(upstream side) of the bowl surface part 12 is larger than theinclination angle θ2 of the surface on the right side (downstream side)thereof. Due to this, the branch stream F2 that tends to flow on theimaginary line V is drawn into the recessed part 14 side, so that theflush water is prevented from arriving at the region A linearly from thefirst water discharge port 21. Further, the flush water on the imaginaryline V is drawn to the recessed part 14 side, whereby a force forenergizing a swirl in a counterclockwise direction is applied to thebranch stream F2, so that the branch stream F2 is caused to join on afurther downstream side. Thus, in some embodiments, it is realized thatthe joining part J is located on the downstream side of the region Awhere the height of the main stream F1 is maximum. Further, the branchstream F2 that tends to flow on the imaginary line V is dropped into therecessed part 14 side, whereby the water amount of the branch stream F2arriving at the joining part J is reduced and accordingly the waterforce and flow rate are reduced. As a result, the impact when the branchstream F2 joins the main stream F1 is moderated, thereby reliablypreventing scattering of the flush water to the outside of the toiletbowl 10.

Further, in the branch stream F2, a component that tends to arrive atthe region A linearly from the first water discharge port 21, that is, acomponent that tends to enter the surface of the erected surface part 11with a large entry angle and tends to collide against the surface, runsdown to the recessed part 14 side or the water force thereof isweakened, with the result that formation of a swirling flow is prompted.Due to this, when joining the main stream F1, the branch stream F2 whichhas become a swirling flow has a smaller entry angle with respect to thesurface of the erected surface part 11, so that the branch stream F2 cansmoothly join the main stream F1 flowing along the erected surface part11. Therefore, the impact when the branch stream F2 joins the mainstream F1 is further moderated, thereby more reliably preventingscattering of the flush water to the outside of the toilet bowl 10.

Further, as shown in FIGS. 1 and 2, the flush water forms at least twowater streams, i.e., the first water stream F3 and the second waterstream F4, and runs down into the recessed part 14. The first waterstream F3 flows from the front part of the toilet bowl 10 into therecessed part 14. The second water stream F4 flows from the rear part ofthe toilet bowl 10 into the recessed part 14 and swirls in the verticaldirection within the recessed part 14. Specifically, as shown in FIG. 7,the second water stream F4 having flowed into the recessed part 14 fromthe rear side of the toilet bowl 10 becomes an ascending stream on thefront side of the recessed part 14 and swirls upward, and then becomes adescending stream again on the rear side of the recessed part 14, thusswirling in the vertical direction, and enters the drain pipe 30.

In a region of the bowl surface part 12 where the first water stream F3runs down, a step part 12A which is stepped in the vertical direction isformed. As shown in FIGS. 7 and 8, the step part 12A is formed in thelower part of the bowl surface part 12, and the recessed part 14 iscontinued below the step part 12A. The step part 12A changes the flowdirection of the first water stream F3. Specifically, the step part 12Aacts so as to separate the first water stream F3, which tends to flowalong the surface of the bowl surface part 12, from the surface of thebowl surface part 12 on the downstream side thereof. In someembodiments, the step part 12A is formed by recessing the surface of thebowl surface part 12 in a concave shape. The step part 12A is formedextending in the horizontal direction along the surface of the bowlsurface part 12. In some embodiments, the step part 12A has apredetermined width in the horizontal direction. According to thisconfiguration, it is possible to cope with the first water stream F3which may flow down spreading in the horizontal direction along thesurface of the bowl surface part 12 or may change flow-down position dueto variations in water force and the like.

As shown in FIG. 8, in the flow of the second water stream F4 swirlingwithin the recessed part 14 in the vertical direction, the flow swirlingupward is formed below the step part 12A. On the other hand, the firstwater stream F3 runs down from above the step part 12A. The first waterstream F3 running downward passes through the step part 12A and therebythe flow direction thereof is changed, so that collision thereof againstthe second water stream F4 is avoided. The second water stream F4 havingascended from below the step part 12A descends inside the recessed part14 and enters the drain pipe 30. In addition, the first water stream F3passes through the step part 12A and thereby the flow direction thereofis changed to substantially the same direction as the flow direction ofthe second water stream F4, and thus the first water stream F3 joins thesecond water stream F4. Accordingly, the second water stream F4 canenter the drain pipe 30 while the water force is maintained. Therefore,the capability of pushing excrement from the recessed part 14 into thedrain pipe 30 is improved as compared with the case where the waterforce is weakened by the collision between the first water stream F3 andthe second water stream F4.

As described above, the step part 12A has an action of separating thefirst water stream F3 passing therethrough from the surface of the bowlsurface part 12, but it is not necessary to separate the whole amountthereof. A part of the first water stream F3 passing through the steppart 12A may flow along the surface of the bowl surface part 12.

Further, the first water stream F3 having passed through the step part12A joins the second water stream F4 within the recessed part 14 andenters the drain pipe 30. As described above, the first water stream F3passes through the step part 12A so that the flow direction thereof ischanged. As a result, the water force of the first water stream F3 isweakened and the flow rate is reduced. However, the cross-sectional areathereof is increased instead, with the result that the first waterstream F3 having an increased thickness flows into the recessed part 14.Therefore, the capability of pushing excrement into the drain pipe 30from the recessed part 14 is further improved.

As described above, in the flush toilet 1 of the present example, theflush water discharged from the water discharge ports 21, 22 flowshaving two water streams, i.e., the main stream F1 and the branch streamF2, and these two water streams join at the joining part J on thedownstream side. Among the two water streams, the main stream F1, whichis a water stream along the erected surface part 11, arrives at thejoining part J earlier than the branch stream F2 at the beginning ofdischarge of the flush water. For this reason, the water stream composedof the main stream F1 is formed in advance at the joining part J beforethe branch stream F2 joins the main stream F1. As a result, the branchstream flowing from the central direction of the toilet bowl 10 towardthe outer circumferential direction (the outward direction of the toiletbowl) can be pressed down by the main stream F1 flowing in theperipheral edge of the toilet bowl 10.

Therefore, the flush toilet 1 can prevent scattering of flush water tothe outside of the toilet bowl 10.

Further, in the flush toilet 1, the joining part J is located on thedownstream side of the region A where the height of the main stream F1is maximum on the front side of the toilet bowl 10. Therefore, it ispossible to prevent the branch stream F2 from affecting the maximumheight of the main stream F1. That is, the main stream F1 flowing in theperipheral edge of the toilet bowl 10 flows while changing its heightdue to the water force, the change in curvature at the peripheral edgeof the toilet bowl 10, and the like. Therefore, if the branch stream F2joins the main stream F1 in the region A where the height of the mainstream F1 is maximum or on the upstream side of the region A, the wateramount, water force, and the like of the branch stream may affect sothat the height of the water stream may exceed the height of the erectedsurface part 11. However, the branch stream F2 is caused to join themain stream F1 on the downstream side of the region where the height ofthe main stream F1 is maximum, thereby making it possible to prevent theinfluence of these factors. Therefore, scattering of flush water to theoutside of the toilet bowl 10 can be reliably prevented.

Further, in the flush toilet 1, the toilet bowl 10 has a recessed part14 provided at the lower end of the bowl surface part 12 and continuedto the drain pipe 30, and the bowl surface part 12 is formed to beinclined in such a manner that the branch stream F2 after the beginningof discharge from the water discharge port 21 is dropped into therecessed part 14 on the imaginary line V connecting the water dischargeport 21 and the region A where the height of the main stream F1 ismaximum in a plan view. According this configuration, since it ispossible to suppress the water amount and the water force of thecomponent of the branch stream F2 that tends to flow on the imaginaryline V, scattering of flush water can be reliably prevented. Further, itis possible to easily adjust the water force and the flow rate of thecomponent of the branch stream F2 that tends to flow on the imaginaryline V according to the inclination angle of the bowl surface part 12,so that the water force or the height of the water stream after joiningcan be easily adjusted, with the result that scattering of flush waterto the outside of the toilet bowl 10 can be reliably prevented.

Further, in the flush toilet 1, the moving distance of the branch streamF2 in a period from when it branches from the main stream F1 to when itarrives at the joining part J is set to be longer than the movingdistance of the main stream F1 in a period from when the branch streamF2 branches therefrom to when the main stream F1 arrives at the joiningJ. Therefore, the main stream F1 can be reliably caused to arrive at thejoining J earlier than the branch stream F2.

The present invention is not limited to the embodiments described above,and, for example, the following embodiments also fall within thetechnical scope of the present invention.

(1) In some embodiments, the step part is provided on the bowl surfacepart, but it is not essential to provide the step part. In someembodiments, the step part extends in the horizontal direction along thesurface of the bowl surface part, but in this case, the length of thestep part is not particularly limited. Further, the extending directionof the step part may be not only the horizontal direction, but also adirection other than the horizontal direction, including the verticaldirection.

(2) In some embodiments, the toilet bowl has a horseshoe-shaped shelfsurface part in a plan view, but this is not essential. Further, whenthe toilet bowl has a shelf surface part, not only the above-describedconfiguration but also other configurations may be adopted, for example,the shelf surface part may be formed over the entire circumference ofthe toilet bowl, or the shelf surface part may be formed in a narrowerrange such as a substantially semicircular shape in a plan view.

(3) In some embodiments, an overhanging part projecting inward from theupper end of the erected surface part is not provided. However, anoverhanging part may be formed in a part of the upper end of the toiletbowl or over the entire circumference of the toilet bowl.

(4) In some embodiments, two water discharge ports are provided, but onewater discharge port or three or more water discharge ports may beprovided. Further, in the case where a plurality of water dischargeports is provided, the second and subsequent water discharge ports arenot necessarily water discharge ports for generating a swirling flow.For example, the water discharge ports may be intended to dischargewater only downward.

(5) In some embodiments, water discharge ports are disposed on the rearside of the toilet bowl, but the positions of the water discharge portsare not particularly limited. In addition, the discharging direction ofthe flush water from the water discharge ports and the swirlingdirection within the toilet bowl according to the discharging directionare also not limited.

(6) In some embodiments, the bowl surface part is inclined in such amanner that the branch stream after the beginning of discharge from thewater discharge port is dropped into the recessed part on the imaginaryline connecting the water discharge port and the region where the heightof the main stream F1 is maximum, in order for the joining part to belocated on the downstream side of the region where the height of themain stream is maximum. However, it is not essential that the joiningpart is located on the downstream side of the region where the height ofthe main stream is maximum.

(7) In some embodiments, the step part is formed by recessing thesurface of the bowl surface part in a concave shape, but the step partmay be formed by bulging the surface of the bowl surface part in aconvex shape.

(8) In some embodiments, the moving distance of the branch stream in aperiod from when the branch stream branches from the main stream to whenit arrives at the joining part is set to be longer than the movingdistance of the main stream in a period from when the branch streambranches therefrom to when the main stream arrives at the joining part.However, this is not essential.

(9) In some embodiments, the recessed part is continued below the steppart, but the step part may be formed at a position separated from therecessed part above the lower end of the bowl surface part as long asthe first water stream flows away from the surface of the bowl surfacepart into the recessed part.

1. A flush toilet comprising: a toilet bowl comprising an erectedsurface part extending in a vertical direction at an upper end part ofthe toilet bowl and a bowl surface part below a lower end of the erectedsurface part to an inner circumferential side; and a water dischargeport opened in the erected surface part and configured to dischargeflush water into the toilet bowl, wherein the flush water forms at leasttwo water streams, the at least two water streams comprising a mainstream flowing in a peripheral edge of the toilet bowl along the erectedsurface part and a branch stream branching from the main stream andrunning down to the bowl surface part side, wherein the branch streamjoins the main stream at a joining part on a downstream side, andwherein the main stream arrives at the joining part earlier than thebranch stream.
 2. The flush toilet of claim 1, wherein the joining partis located on a downstream side of a region where a height of the mainstream is greatest on a front side of the toilet bowl.
 3. The flushtoilet of claim 1, wherein the toilet bowl comprises a recessed partcontinued from a lower end of the bowl surface part to a drain pipe, andwherein the bowl surface part is inclined in such a manner that thebranch stream after a beginning of discharge from the water dischargeport is dropped into the recessed part on an imaginary line connectingthe water discharge port and the region where the height of the mainstream is greatest in a plan view.
 4. The flush toilet of claim 1,wherein a moving distance of the branch stream in a period from when thebranch stream branches from the main stream to when the branch streamarrives at the joining part is set to be longer than a moving distanceof the main stream in a period from when the branch stream branchestherefrom to when the main stream arrives at the joining part.